1. Technical Field
The present invention relates to semiconductor devices. Specifically, the present invention relates to a semiconductor device in which a semiconductor element such as a sensor chip including a diaphragm is mounted on a substrate.
2. Background Art
FIG. 1 is a schematic cross-sectional view showing a structure of a conventional semiconductor device. A semiconductor device 11 has a lower surface of a semiconductor element 15 adhered to a die bonding pad 13 arranged on a substrate 12 like a printed wiring board using a die bonding resin 16 (silicone resin). The semiconductor element 15 has a diaphragm 14 laminated on the upper surface of a base 17, where the diaphragm 14 has the four corners fixed to the upper surface of the base 17, and a cavity 18 vertically passes through the base 17 so as not to inhibit the displacement or the vibration of the diaphragm 14. In the illustrated example, the upper half of the cavity 18 is a truncated pyramid shape, and the lower half is a reversed truncated pyramid shape, but the entire cavity 18 may be a truncated pyramid shape or a reversed truncated pyramid shape. The semiconductor device in which the semiconductor element is die bonded on the substrate like the printed wiring board includes a microphone disclosed in patent document 1, and the like.
In the assembly step of such semiconductor device 11, the die bonding resin 16 in the melted state is applied to the die bonding pad 13, the semiconductor element 15 is placed over the die bonding pad 13, and then the die bonding resin 16 is cured to fix the semiconductor element 15 to the substrate 12.
When die bonding the semiconductor element 15 to the substrate 12 in such manner, the die bonding resin 16 in the melted state is sometimes taken up to the upper surface of the base 17. If the die bonding resin 16 is taken up, the die bonding resin 16 enters the gap between the diaphragm 14 and the upper surface of the base 17 and cures thereat, whereby the die bonding resin 16 may fix the diaphragm 14 to the base 17 or may enter the gap between the diaphragm 14 and the base 17 and become a foreign substance. If the diaphragm 14 is fixed to the base 17, the diaphragm 14 cannot vibrate a defined amount and the semiconductor element 15 cannot obtain a predetermined sensitivity. If the die bonding resin 16 is sandwiched between the diaphragm 14 and the base 17 as a foreign substance, the vibration characteristics of the semiconductor element 15 change. The failure thus occurs in the semiconductor device 11 and the yield of the semiconductor device 11 lowers.